diff --git a/core/src/main/java/org/apache/calcite/sql/SqlTimeTzLiteral.java b/core/src/main/java/org/apache/calcite/sql/SqlTimeTzLiteral.java
index 19dd05f..e13a742 100644
--- a/core/src/main/java/org/apache/calcite/sql/SqlTimeTzLiteral.java
+++ b/core/src/main/java/org/apache/calcite/sql/SqlTimeTzLiteral.java
@@ -20,10 +20,10 @@
 import org.apache.calcite.sql.type.SqlTypeName;
 import org.apache.calcite.util.TimeWithTimeZoneString;
 
-import com.google.common.base.Preconditions;
-
 import java.util.Objects;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 /**
  * A SQL literal representing a TIME WITH TIME ZONE value, for example <code>TIME WITH TIME ZONE
  * '14:33:44.567 GMT+08'</code>.
@@ -36,7 +36,7 @@
   SqlTimeTzLiteral(TimeWithTimeZoneString t, int precision,
                              SqlParserPos pos) {
     super(t, true, SqlTypeName.TIME_TZ, precision, pos);
-    Preconditions.checkArgument(this.precision >= 0);
+    checkArgument(this.precision >= 0);
   }
 
   //~ Methods ----------------------------------------------------------------
diff --git a/core/src/main/java/org/apache/calcite/sql/SqlTimestampTzLiteral.java b/core/src/main/java/org/apache/calcite/sql/SqlTimestampTzLiteral.java
index 0e79038..d10ba74 100644
--- a/core/src/main/java/org/apache/calcite/sql/SqlTimestampTzLiteral.java
+++ b/core/src/main/java/org/apache/calcite/sql/SqlTimestampTzLiteral.java
@@ -20,10 +20,10 @@
 import org.apache.calcite.sql.type.SqlTypeName;
 import org.apache.calcite.util.TimestampWithTimeZoneString;
 
-import com.google.common.base.Preconditions;
-
 import java.util.Objects;
 
+import static com.google.common.base.Preconditions.checkArgument;
+
 /**
  * A SQL literal representing a TIMESTAMP WITH TIME ZONE value, for example <code>TIMESTAMP
  * '1969-07-21 03:15 GMT+00:00'</code>.
@@ -35,7 +35,7 @@
 
   SqlTimestampTzLiteral(TimestampWithTimeZoneString ts, int precision, SqlParserPos pos) {
     super(ts, false, SqlTypeName.TIMESTAMP_TZ, precision, pos);
-    Preconditions.checkArgument(this.precision >= 0);
+    checkArgument(this.precision >= 0);
   }
 
   //~ Methods ----------------------------------------------------------------